In the field of data transmission, it is often desirable to use existing communication transmission infrastructure to transmit data to a desired destination. One area in which this is becoming increasingly desirable is the broadcast communication industry. Accordingly, datacasting, the point to multipoint delivery of data using the broadcast spectrum, is an increasingly important area in the field of data transmission. Technologies such as MPEG-2 have made possible the transmission of coded digital video and audio over the broadcast spectrum. In datacasting, data is multiplexed along with coded video and audio data.
Two modes of datacasting are commonly used: constant bit rate datacasting and opportunistic datacasting. Constant bit rate datacasting operates by taking away some bandwidth from traditional programming to deliver data at a constant rate. Opportunistic datacasting takes advantage of inherent inefficiencies of spectrum usage by replacing null packets with data. To see why inefficiencies may arise, consider an example where a 19.39 Mbits/second channel is used to deliver high definition programming. When encoding a football game using MPEG-2, the encoded video and audio data may use up the entire channel. On the other hand, a less active program may use between 17 and 19.39 Mbits/second depending on instantaneous scene activity. Typically, the remaining bandwidth is filled with null packets. Using opportunistic datacasting, this may be replaced with data packets.
Datacasting enables broadcasters to realize new revenues with existing spectrum. As an example, a broadcaster can transmit a newspaper to subscribers during off peak hours when the entire channel is not being used for traditional video services. Other potential applications include play along games, sports statistics, enhanced advertising, corporate communications, local weather and emergency information, coupons, ebooks, mp3 audio, low bit rate mpeg-4 video, software, newsgroups, magazines and news downloads.
While opportunistic datacasting improves the efficiency of a broadcast channel by reclaiming lost bandwidth, a major problem with it is the lack of quality of service (QOS) guarantees. Since opportunistic datacasting only replaces existing null packets (which occur at random), no guarantees on throughputs can be made. Using constant bit rate datacasts on the other hand, lowers the quality of traditional video services since it takes bandwidth away.
Therefore, it is evident that there is a need in the art for systems and methods for providing on-demand datacasting with a QOS guarantee.